1. Field of the Invention
The present invention relates to a method and apparatus for separating a welding electrode tip from a workpiece when the electrode tip has temperature adhered the workpiece.
2. Description of the Prior Art
Automobile body panels are spot welded using a welding apparatus which includes a general purpose robot having six degrees of freedom and a spot-welding gun coupled to a wrist portion of the robot. The conventional spot-welding gun pressurizes a workpiece between a pair of electrode tips by reciprocally moving one of the electrode tips by an air cylinder. By comparison, a servo-welding gun having a pair of electrode tips, one of which is driven by a servo motor, was proposed by the present applicant in Japanese Patent Application No. 4-94916 filed on Mar. 23, 1992.
When temperature adhesion has occurred between an electrode tip and a workpiece, a worker after recognizing the temperature adhesion enters the welding area to hammer the adhering portion of the electrode tip free from the workpiece. In the case of a welding gun operated by an air cylinder, remaining air pressure continues to bias the electrode tip in a direction away from the workpiece. Consequently, the workpiece will not be injured when the hammered electrode tip is forced to move relative to the workpiece. In the case of a servo-welding gun, however, the servo-welding gun and a robot are automatically powered off when the worker enters the welding area. Therefore, no biasing force acts on the electrode tip in a direction away from the workpiece, and the electrode tip continues to contact the workpiece. Consequently, the workpiece will be injured when the hammered electrode tip is moved laterally relative to the workpiece.